The present invention relates to regulators for agricultural vehicle dispensers and, more particularly, to a regulator that improves the accuracy and reliability of applying agricultural chemicals to fields and planting seeds.
It is common practice in the agricultural industry to use electronically controlled implements for applying chemicals to fields and for planting seeds. This practice allows agricultural workers to drive the motive vehicle (tractor) at various speeds according to field conditions, yet have the application rate remain at the selected value. This practice also allows the agricultural worker to change the application rate by entering a new application rate value so as to optimize the application rate for field condition, such as various soil productivity data.
The term xe2x80x9capplication ratexe2x80x9d is defined as the ratio of the amount of chemical(s) or seed in appropriate units to an appropriate standard unit of distance (or area) traversed by the implement that is applying the chemical(s) or planting seeds. For example, the application rate might be 200 pounds of anhydrous ammonia per acre, or it might be ten seeds per foot in each of 60 rows.
Maintaining optimum application rates for agricultural chemicals and seeds is economically important. If too much chemical is applied, the cost of the excess chemical will be lost, and possibly the plants and/or the soil could be damaged by the excess chemical. If too little chemical is applied, productivity (yield) will decrease and potential income will also be lost. Similarly, if seeds are planted too close or too distant, productivity and income will be lost. The application rates of some chemicals, such as herbicides and insecticides, are mandated in law.
The earliest techniques for controlling application rates for mechanized agricultural implements included various mechanical mechanisms, such as combinations of gears, chains, shafts, and related machine design elements that are operated off a wheel or axle of the implement in a direct drive fashion. One classic example of a pre-electronic agricultural dispensing implement is the manure spreader. Direct drive dispensing implements are subject to wheel slippage. The dispensing (application) rates of some of the implements were adjustable and others were not adjustable.
More recent dispensing technology for agricultural implements included a combination of various wheel speed sensors and electronically controlled dispensing devices. Using this technology, a wheel speed sensor produces an electronic signal that is received by a dispensing device on an agricultural implement. The signal from the wheel speed sensor is typically a stream of voltage pulses, the frequency of which represents the speed of the wheel. The dispensing device applies chemical or plants seeds at a rate that is proportional to the speed that is sensed by the wheel speed sensor. Typically the sensor is a shaft encoder that is attached to the tractor""s axle, drive shaft, or power-take-off (PTO) shaft, although the wheel speed sensor could be mounted similarly on the implement pulled by the tractor
Manufacturers of tractors, implements, and after-market devices have formed industry standards (protocols) for the electronic pulse trains that are produced by the wheel sensors and for the electronic cabling and connectors that are used in the technology. The standards resulted in wide spread compatibility that has benefitted the agriculture industry.
The wheel speed sensors discussed above have several deficiencies. The wheel speed sensor senses the wheel rotation rates, but not the actual speed of the implement over ground, which is critical to accurate dispensing rates. Wheel speed sensors produce inaccurate results due to wheel slippage, uneven ground conditions, and wheel size changes from wear or build up of mud and soil on the tire tread.
Ground speed sensing in the agriculture industry became available with the advent of Doppler radar speed sensors, as disclosed in U.S. Pat. Nos. 4,633,252 and 3,895,384. This technique is immune to the errors that are introduced by wheel slippage, change in wheel size, and differing wheel speeds in turns. However, Doppler radar speed sensors have their own deficiencies. Movement of obstructions in the microwave beam""s path, such as grass moving in the wind and soil shifting due to the tractor""s or implement""s motions, can affect these speed sensors. The microwave radiation that the Doppler radar speed sensor uses presents potential biological hazards, as disclosed in FCC OET Bulletin 56, Questions and Answers about Biological Effects and Potential Hazards of Radiofrequency Electromagnetic Fields, August 1999.
Furthermore, the means and location of mounting the radar speed sensor pose problems. The angular direction of the radar microwave beam must be within two (2) degrees and the sensor must be mounted 30 to 36 inches above the ground. Doppler radar works best in direct line-of-sight measurement. Since such direct line-of-sight is not practical for agricultural vehicles and implements, the technique is not optimally applied. For agricultural applications, Doppler radar speed sensors must be mounted well above the ground level and they must be capable of compensating for the difference between theoretical ground speed and sensed ground speed. Mathematically, the two speed measurements differ due to the cosine of the angle between the ground plane and the incidence of the radar beam. When the ground plane varies, such as over varying field terrain, an error is introduced into the speed measurement. Practicioners in Doppler radar technology know this error as the cosine error. Every momentary variation in the radar sensor location, such as by vibration or flexing of the vehicle, and every momentary variation in the target location, introduces error into the speed measurement.
Given the relatively rough conditions of typical agricultural lands, the prior art does not satisfy the needs of the agriculture industry for an accurate and reliable means of measuring true ground speed for the purpose of achieving optimal application rates for agricultural chemicals and the planting of seeds.
The disadvantages of the prior art are overcome by the present invention, and an improved regulator from an agricultural vehicle dispenser and a method are hereinafter disclosed for more reliably applying agricultural chemicals to fields and for more reliably planting seeds.
According to the present invention, there is provided a speed-over-ground (SOG) sensor that receives position, speed, altitude, and other related data from the Global Positioning System of Earth-orbiting satellites and, based on that data, creates and conditions a stream of voltage pulses that accurately and reliably represents the true SOG of the sensor to industry-standard control circuits of agricultural chemical dispensing implements and seed planters.
It is therefore an object of the present invention to provide an improved speed-over-ground (SOG) regulator which utilizes GPS technology for use with agricultural chemical dispensing implements and seed planters.
A feature of the present invention is to provide an improved SOG regulator that is compatible with the cabling, connectors, and electronic signal protocol(s) of industry-standard control circuits of agricultural chemical dispensing implements and seed planters.
It is a feature of the present invention that the SOG sensor may be portable, and thus may be easily transferred between tractors or to other vehicles.
Yet another feature of the invention is that the regulator may be calibrated to a given control system one time. Continuous recalibrations which are commonly used in radar sensor systems are not required.
It is a further feature of the invention that the speed sensor does not present any radiation dangers, and accordingly the sensor need not be disabled when stationary.
Another feature of the invention is that the speed sensor is impervious to blowing grass, weeds, crops or sifting soil. The speed sensor is not affected by operational vibration and does not require rigid mounting to the vehicle to minimize or prevent vibration.
These and further objects, features, and advantages of the present invention will become apparent from the following detailed description, wherein reference is made to the figures in the accompanying drawings.